ИСТИНА

Objective Diffusion tensor tractography (DTT) is an effective imaging technique for visualization of cranial nerves, and can be particularly useful in patients with vestibular schwannomas (VSs). There is however limited data concerning the effectiveness of DTT for reconstruction of facial nerve (CN VII) and its relationship with 3D tumor reconstruction. This is particularly true in Koos 3 and 4 tumors where there is greater difficulty in visualization of the cranial nerves. Methods DTT and anatomical images obtained on 3T­MRI were used to build individual tumor­cranial nerve models. Preprocessing of the images is necessary, which included motion correction. Tumor model reconstruction and tractography were performed using 3D­Slicer software platform. Regions of interest (ROIs) were placed on anteriosuperior, anteromedial anteroinferior and posterior of the tumor model and visualization of the tracts was done with the help of fiducial markers. CN VII tracts were reconstructed in cases of Koos grade 3­4 VSs (tumors filling the cerebellopontine cistern). The cut­off point for building the tracts was diameter of the tumor exceeding 4 cm due to distortion of the facial nerve and it’s thinning. Conclusion DTT is a powerful tool for reconstructing of CN VII fibers in patients VS. The best results are obtained in tumors less than 4 cm. Giant VS result in extensive distortion which adversely affects reconstruction. Instead, small (Koos 1­2) tumors the visualization of CN VII is also complicated due to the short, straight course of the nerve, Good anatomical preservation of CN VII and presence of a cleavage plane between the nerve and a tumor in Koos 1­2 VSs surgery, makes necessity of DTT implementation in these cases qestionable.